April’s debut of the Rock ’n’ Roll Marathon brought an $8.13 million boost to the local economy, according to a study commissioned by the race organizers.

The study’s findings, released Tuesday, far exceed the $2 million in tourism spending projected when the race was announced in 2013. The report met with skepticism from some businesses that didn’t notice a big sales boost and from critics of the event who questioned the study’s methodology.

Scott Dupree of the Greater Raleigh Sports Alliance said the report shows Rock ’n’ Roll was worth the effort for Raleigh.

“The numbers are even better than we had originally estimated,” Dupree said. “The economic impact and the tax collection validates what we thought all along – that the Rock ’n’ Roll Marathon Series would be a wonderful event for Raleigh and that it would provide our community with a major economic boost.”

Rock ’n’ Roll hired Scott Minto, a researcher at San Diego State University, to survey marathon participants about how much they spent in Raleigh. Based on responses from 4,400 runners, Minto estimates that nearly half the visitors from outside Wake County stayed in hotels, accounting for 3,076 runners and 4,768 spectators. About half of the 10,918 registered runners live in Wake.

That meant that 3,692 hotel rooms were occupied the night before the race, according to the report, for total hotel spending of $1.02 million.

Minto estimates the out-of-town visitors spent $3.26 million on meals, entertainment, transportation and shopping while in Raleigh. And race organizers and expo vendors spent $890,000 here to pull off the event.

Some businesses around the race route said they didn’t see a jump in business. Across from the finish line on Fayetteville Street, La Volta Italian restaurant hosted a post-race party for 100 people, general manager Michael Longo said.

But Longo said that boon was offset by an unusually light dinner crowd on Saturday night before the marathon. The street in front of the restaurant was already blocked to prepare for the event, keeping some regulars away.

“We only got a few racers in here to carb up” Saturday night, Longo said.

And on Hillsborough Street, traffic was blocked through early Sunday afternoon as runners passed by. Reader’s Corner owner Irv Coats said sales for the day dropped more than 20 percent. Coats didn’t notice any runners or spectators drop in to browse the shelves.

“It didn’t help,” he said of the race. “The day was pretty much a bust.”

But according to Minto’s survey, visitors reported spending an average of $103.53 per day per person in addition to their hotel rooms. Of that, they spent $49.59 on food and drink and $24.53 in local shops.

Minto added $2.69 million to the total economic impact for what he calls “indirect and induced impact.” That represents spending by businesses that benefited from the race. “That’s a function of how the spending has a ripple effect in the local economy,” he said.

Jim Micheels of the City of Oaks Marathon said he’s skeptical of Minto’s figures because the researcher is paid by Rock ’n’ Roll. “It’s not a reliable study,” Micheels said. “It has to be from a third party.”

Minto defended his data, saying he uses a “consistent” approach for evaluating endurance events across the country. He pointed out that hotel occupancy rates aren’t a reliable barometer because it’s impossible to isolate marathon-related guests from other visitors.

His economic impact estimates have varied for Rock ’n’ Roll events across the country. When the race debuted in Savannah, Ga., in 2011, the marathon had nearly twice as many runners as Raleigh’s event. Minto’s report pegged the economic impact of that race at $32.3 million.

Rock ’n’ Roll will return to Raleigh in April for the next four years. Some businesses are hoping they’ll be left off the race course next year.

“Our business is based on regulars, not the mythical people who are supposed to be coming to Raleigh for the races,” said David Sullivan, who owns Cup A Joe on Hillsborough Street.